1. Technical Field of the Invention
The present invention relates to position detecting devices for detecting motional positions of objects to be detected and, more particularly, to a useful device that is employed in a device etc., for detecting a rotational angle (angular position) of a crankshaft or other members of, for instance, an on-vehicle engine.
2. Related Art
In the related art, a position detecting device of such a type, i.e., more particularly, a device disclosed, for instance, in U.S. Pat. No. 4,233,592 has heretofore been known as a device for detecting a rotational angle of a crankshaft of an engine. With such a device, a gear type rotor, mounted on and rotatable with the crankshaft, has one area formed with a notched portion, which is detected by a rotary angular sensor disposed in close proximity to the rotor for detecting a passage of each tooth for thereby detecting the notched portion based on which the rotational angle (angular position) of the rotor (crankshaft) is detected as a reference on the detected portion.
The other position detecting device of such a type includes a device that is disclosed in, for instance, Japanese Patent No. 2570442. This device is configured in a way to detect a rotational angle of the crankshaft of the engine, described above, in conjunction with a rotational angle of a camshaft mechanically connected to the crankshaft through a belt or a chain or the like. The device includes a sensor, detects the presence of a given angular position every time the rotational angle of the camshaft lies at the given angular position, and discriminate a combustion cylinder of the engine based on contrast between detection output of the sensor and a reference angle of the crankshaft.
Either way with these devices, the rotational angle of the crankshaft or camshaft is detected in such a way to allow detected angle information to be provided to operational control of the engine, by which operations are executed to maintain appropriate controls of a fuel injection timing and an ignition timing or the like.
By the way, in recent years, attempts have heretofore been made to perform control to temporarily stop the engine during a halt of a vehicle when waiting for the traffic light to change with a view to improving fuel consumption and reducing exhaust emissions. However, during stopping operations of the engine, rapid drop or unstable status usually tend to occur on a rotational speed of the crankshaft, resulting in deterioration in reliability of angle information, mentioned above, which is detected under such defective circumstances. That is, a difficulty is encountered in properly detecting even the notched portion, playing a role as a reference of angle information, of the rotor, resulting in an increase in probability of causing defects wherein the presence of the notched portion is detected at a rotational angle (angular position) in the absence of the notched portion. Also, such control undergoes defects wherein during restart of the engine, angle information cannot be provided for operational control of the engine unless the notched portion of the rotor is detected, suffering inevitable deteriorations in startability or degradation in emissions.
Also, not only the device, configured to detect the rotational angle of the detection object including the crankshaft or the camshaft (that is exactly a rotor mounted on each of the shafts), but also the device, associated with a detection object provided with a specified reference position to allow the reference position to be detected for deriving a motional position, undergo actual situations generally common to each other. That is, under circumstances where a difficulty is encountered in detecting the reference position due to the occurrence of unstable status in the motion speed of the detection object or a halt of the detection object in motion, inevitable deterioration occurs in reliability related to relevant positional information.